1. Field of the Invention
The present invention relates generally to a YIG (yttrium iron garnet) oscillator and a method of manufacturing the same and, more particularly, to a broadband variable-tuned type YIG oscillator utilizing a YIG crystal as a resonator and a method of manufacturing the same.
2. Description of the Related Art
One example of the conventional variable-tuned type YIG oscillator utilizing a YIG crystal (YIG device) as a resonator is illustrated in FIG. 6 which shows particularly the resonance circuit portion, in an enlarged view, of the variable-tuned type YIG oscillator. The illustrated YIG oscillator comprises a substrate 4 having predetermined circuit patterns (metallic layers) 6 formed thereon which comprise the wiring of the oscillator circuit, a YIG crystal 1 having a ball-like shape in this example (hereinafter referred to as YIG crystal ball) separate from the substrate 4 and located at a predetermined position on the substrate 4, and amplifier element 2 separate from the substrate 4 and also located at a predetermined position on the substrate 4. The substrate having predetermined circuit patterns (metallic layers) formed thereon such as the substrate 4 is hereinafter referred to as xe2x80x9ccircuited substratexe2x80x9d.
Fixed to the YIG crystal ball 1 is a support rod 11 which determines the location of the YIG crystal ball 1 on the circuited substrate 4. Further, the amplifier element 2, which has three terminals in this example, has its three terminals electrically connected by wire bonding to the associated three circuit patterns 6 formed around the amplifier element 2. That is, the terminals of the amplifier element 2 are electrically connected to the circuit patterns 6 through the bonding wires 5.
Surrounding the YIG crystal ball 1 in spaced relation therewith is a generally semicircular coupling loop (conductor wiring for electrically and magnetically coupling between the YIG crystal ball 1 and the electric circuit) 3, the opposite ends of which are electrically connected as by soldering to the circuit patterns 6 formed around the YIG crystal ball 1. Through this coupling loop 3, the YIG crystal ball 1 is electromagnetically coupled to the wiring of the oscillator circuit including the amplifier element 2. More specifically, the coupling loop 3 and the YIG crystal ball 1 are magnetically coupled with each other, and the coupling loop 3 is electrically coupled to the wiring of the oscillator circuit. The coupling loop 3 thus serves as a conductor for magnetic resonance and electrical connection.
Since the variable-tuned type YIG oscillator is an oscillator which will generate signals with frequencies in the extremely high frequency microwave range, it is to be noted that parasitic components in the resonance circuit have significant effects on the oscillating characteristics. With the prior art variable-tuned type YIG oscillator as constructed as described above, the resonance circuit has been heretofore formed by the following assembly and wiring operations involving:
(1) fixing the YIG crystal ball 1 to the support rod 11 which is a support member;
(2) locating the amplifier element 2 at a predetermined position on the circuited substrate 4 and electrically connecting its three terminals to the corresponding circuit patterns 6 respectively which constitute the wiring of the oscillator circuit;
(3) locating the semicircular coupling loop 3 at a predetermined position on the circuited substrate 4 and electrically connecting the opposite ends of the coupling loop 3 to the corresponding circuit patterns 6 respectively; and
(4) locating the YIG crystal ball 1 inside of the semicircular coupling loop 3 by means of the support rod 11 and adjusting the position of the ball, followed by fixing the support rod 11 to the circuited substrate 4 to thereby fix the YIG crystal ball 1 in place.
It can thus be understood that the conventional operations of locating the separate coupling loop 3 and amplifier element 2 on the circuited substrate 4 and then electrically connecting them to the circuit patterns 6 by soldering and wire bonding as discussed above have been inevitably accompanied in the process of manufacture with mechanical variations or unevenness in the position of connection of the bonding wires 5, the position of connection of the coupling loop 3 and the relative position between the YIG crystal ball 1 and the coupling loop 3.
Particularly, the position of connection of the coupling loop 3 and the relative position between the YIG crystal ball 1 and the coupling loop 3 are attended with wider mechanical variations or unevenness as compared to the position of connection of the bonding wires 5.
These mechanical variations in turn cause variations in parasitic components in the resonance circuit. The higher the oscillating frequencies of the oscillator, the greater the effects the parasitic components will exert on the oscillating characteristics of the oscillator. Especially in the oscillator such as the YIG oscillator which produce frequencies in the microwave range, even a slight variation in the parasitic components can possibly lead to a significant change in the oscillating characteristics of the oscillator. Since even slight mechanical variations in manufacture can exert significant influences on the oscillating characteristics of the oscillator, it is thus to be understood that the conventional YIG oscillator had the drawback of low manufacturing yields.
Accordingly, it is an object of the present invention to provide a method of manufacturing a variable-tuned type YIG oscillator accompanied with substantially no mechanical variations in the resonance circuit.
It is another object of the present invention to provide a method of manufacturing a variable-tuned type YIG oscillator which allows for improving manufacturing yields of YIG oscillators.
It is still another object of the present invention to provide a variable-tuned type YIG oscillator substantially free from mechanical variations in the resonance circuit.
It is yet another object of the present invention to provide a variable-tuned type YIG oscillator requiring substantially no operations for assembly and wiring of the resonance circuit.
In order to accomplish the aforesaid objectives, in a first aspect of the present invention, a method of manufacturing a YIG oscillator is provided which comprises the step of forming a coupling loop of a thick film conductor on a substrate having a predetermined circuit pattern formed thereon; the step of forming a hole for positioning a YIG crystal at a predetermined position inside of the coupling loop in the substrate from the front surface of the substrate; and the step of fitting the YIG crystal ball in the hole.
In a first preferred embodiment, the substrate is a semiconductor substrate, and the method includes the step of integrating active elements, passive elements, the circuit pattern, and the coupling loop of the oscillator circuit portion of the YIG oscillator monolithically on the face of the semiconductor substrate by the monolithic microwave integrated circuit manufacturing technique.
The circuit pattern is formed by photoetching technique as a predetermined- pattern on the semiconductor substrate having the active elements and the passive elements integrated thereon, the coupling loop is, after the formation of the circuit pattern, formed as a thick film conductor shaped so as to surround at least a portion of the outer periphery of the YIG crystal on the semiconductor substrate.
The coupling loop is formed by electrolytic plating process as a thick film conductor on one circuit pattern formed on the semiconductor substrate.
The hole is formed by etching technique on the semiconductor substrate having the active elements, the passive elements, the circuit pattern and the coupling loop monolithically integrated thereon from above the front surface of the substrate.
The method may further include the step of reducing the thickness of the semiconductor substrate by polishing the back surface of the substrate.
In a second preferred embodiment, the substrate is a dielectric substrate, and the method includes the step of mounting active elements and passive elements of the oscillator circuit portion of the YIG oscillator on the face of the dielectric substrate, the step of forming the circuit pattern as a predetermined pattern on the dielectric substrate having the active elements and passive elements mounted thereon, and the step of forming the coupling loop as a predetermined shape on the dielectric substrate having the active elements and passive elements mounted thereon.
The circuit pattern is formed by photoetching technique as a predetermined pattern on the dielectric substrate having the active elements and the passive elements mounted thereon, and the coupling loop is, after the formation of the circuit pattern, formed as a thick film conductor shaped so as to surround at least a portion of the outer periphery of the YIG crystal on the dielectric substrate.
The coupling loop is formed by electrolytic plating process as a thick film conductor on one circuit pattern formed on the dielectric substrate.
The hole is formed by etching technique in the dielectric substrate having the active elements, the passive elements, the circuit pattern and the coupling loop integrated as a hybrid integrated circuit thereon from above the front surface of the substrate.
The method may further include the step of reducing the thickness of the dielectric substrate by polishing the back surface of the substrate.
In each of the embodiments described above, the method may include the step of maintaining the environment surrounding the substrate at a predetermined temperature prior to the step of fitting the YIG crystal in the hole.
In a second aspect of the present invention, a YIG oscillator is provided which comprises a substrate having active elements, passive elements, a circuit pattern and a coupling loop integrated thereon to form the oscillator circuit portion of the YIG oscillator; a hole for positioning a YIG crystal at a predetermined position inside of the coupling loop, the hole being formed in the substrate from the front surface of the substrate; and a YIG crystal fitted in the hole.
In a first preferred embodiment, the substrate is a semiconductor-substrate, and the semiconductor substrate has the active elements, the passive elements, the circuit pattern, and the coupling loop of the oscillator circuit portion of the YIG oscillator integrated monolithically on the face thereof by the monolithic microwave integrated circuit manufacturing technique.
The circuit pattern is formed by photoetching technique as a predetermined pattern on the semiconductor substrate having the active elements and the passive elements integrated thereon., and the coupling loop is formed as a thick film conductor shaped so as to surround at least a portion of the outer periphery of the YIG crystal on the semiconductor substrate.
The coupling loop is formed by electrolytic plating process as a thick film conductor on one circuit pattern formed on the semiconductor substrate.
The hole is formed by etching technique on the semiconductor substrate having the active elements, the passive elements, the circuit pattern and the coupling loop monolithically integrated thereon from above the front surface of the substrate.
In a second preferred embodiment, the substrate is a dielectric substrate. The active elements and the passive elements of the oscillator circuit portion of the YIG oscillator are mounted on the face of the dielectric substrate, and the circuit pattern is formed as a predetermined pattern on the dielectric substrate having the active elements and passive elements mounted thereon, and the coupling loop is formed as a predetermined shape on the dielectric substrate having the active elements and passive elements mounted thereon.
The circuit pattern is formed by photoetching technique as a predetermined pattern on the dielectric substrate having the active elements and passive elements mounted thereon, and the coupling loop is formed as a thick film conductor shaped so as to surround at least a portion of the outer periphery of the YIG crystal on the dielectric substrate.
The coupling loop is formed by electrolytic plating process as a thick film conductor on one circuit pattern formed on -the dielectric substrate.
The hole is formed by etching technique in the dielectric substrate having the active elements, the passive elements, the circuit pattern and the coupling loop integrated as a hybrid integrated circuit thereon from above the front surface of the substrate.
The YIG oscillator constructed as set forth above may be used with spectrum analyzers, network analyzers and the like, whereby the analyzing accuracy of the equipment may be markedly improved.